Cable systems normally include a plurality of discrete cable lengths which are joined together at splice locations and which are joined to other apparatus at terminal points. Each of these discrete cable lengths comprises a multi-conductor core that is enclosed in a metallic shield, and an outer plastic jacket. The electrical shield normally takes the form of an aluminum tape that is wrapped longitudinally about the core to form a tubular member having an overlapped seam.
A metallic shield in telephone cables performs a variety of important functions. Some of these are protection of installers from injury and equipment from damage if a live power line should fall and contact the cable, protection from inductive pickup due to power line voltage, protection from lightning, and suppression of radio frequency pickup. The metallic shield also provides physical protection of the cable core and acts as a barrier to moisture penetration.
To obtain effective shielding from power-line-induced noise, for example, shield continuity must be provided throughout the cable. At splice locations where the cable jacket and shield are removed to expose the individual conductors, it is necessary to provide for continuity of the electrical shield across the splice locations for proper electrical protection of the conductors. Moreover, it is not uncommon for a cable shield to be earth grounded. Connection to the cable shield at splice locations is generally accomplished with a shield clamping device which is referred to in the art as a bond clamp or bonding device.
One prior art bonding device for use in providing electrical cable shield continuity clamps directly onto the relatively thin shield alone; however, such a device tears or damages the thin conductive shield and thereby loses its effectiveness. Another bonding device includes a base which fits beneath the shield and which has a stud protruding outwardly through a slit which is cut in the shield and in the outer jacket. An outer bridge is mounted on the stud to clamp the shield and jacket between the base and the bridge.
A cable shield connector which overcomes the above-mentioned problems comprises an inner plate having an upstanding tab on one end thereof, and an outwardly protruding threaded stud spaced from the tab. The opposite end of the inner plate is slipped under the shield until the stud abuts the ends of the shield and jacket and an outer plate is positioned on the stud over the jacket and forced toward the inner plate by a nut which is turned along the stud. The outer plate first contacts the upstanding tab of the inner plate and tends to pivot thereabout causing the other ends of the plates to tightly clamp the shield and jacket therebetween. Such a cable shield connector is disclosed and claimed in U.S. Pat. No. Re 28,468 which was reissued on July 8, 1975 in the names of R. G. Baumgartner et al.
Shields are also removed from distribution cables at locations in distribution loops where cable conductors are connected to secondary cables having a relatively small number of conductors and that are run from distribution points to subscribers' premises. These secondary cables which are commonly referred to as service wires also include a metallic shield which is covered by an outer plastic jacket and which is connected electrically to the cable shield. Additional consideration must be given to clamping devices for service wires in that provisions must be made for maintaining the compression on the conductors, notwithstanding the cold flow of the plastic insulation with the lapse of time. This greatly reduces the potential for connections becoming loose and hence failing. Moreover, any universal-type clamp device should have the capacity for accommodating plural wires in a cable closure with provisions for applying substantially equal clamping forces to each of the wires of possibly different size. A clamping device for service wires is shown in U.S. Pat. No. 3,924,920 which issued Dec. 9, 1975 in the names of R. J. Moscioni and G. M. Sellar.
In underground closures, it is not uncommon to clamp service wires to a commercially available device which is then connected electrically in some fashion to an exposed shield of a jacketed distribution cable. These devices generally have a bulky profile and are generally arranged in a random fashion by an installer, thereby adding to the size of the closure. Another commercially available device includes a strip of metallic material having a plurality of spaced openings formed therealong. The strip is wrapped about a shield of a service wire so that a stud of a shield bonding clamp such as that shown in hereinbefore mentioned U.S. Pat. No. Re. 28,468 is caused to extend through overlapped aligned openings of the strip after which a nut is turned along the stud.
Clearly, there is a need for a connecting device which is used to reestablish electrical continuity of a shield across a cable splice and which is capable of connecting electrically and mechanically more than one service wire shield to the cable shield while preventing inadvertent movement of the service wires. Seemingly, the prior art does not show a connector which fulfills these needs.